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Home , Amaltheidae, Amaltheus, Arnioceras, Bredyia, Dumortieria, Grammoceras

Lower and Middle ammonoids of the Group in , and their palaeobiogeographical and biostratigraphical importance

KAZEM SEYED−EMAMI, FRANZ T. FÜRSICH, MARKUS WILMSEN, MAHMOUD R. MAJIDIFARD, and ALI SHEKARIFARD

Seyed−Emami, K., Fürsich, F.T., Wilmsen, M., Majidifard, M.R., and Shekarifard, A. 2008. Lower and ammonoids of the Shemshak Group in Alborz, Iran and their palaeobiogeographical and biostratigraphical importance. Acta Palaeontologica Polonica 53 (2): 237–260.

The Shemshak Group at Shahmirzad (northern Iran) is characterized by the most frequent and extensive marine intercala− tions and contains the most abundant and diverse ammonite faunas hitherto known from the Lower and lower Middle Ju− rassic strata of the Alborz Range. So far, 62 ammonite taxa have been recorded from this area, including 25 taxa from ear− lier studies. The taxa belong to the families Cymbitidae, Echioceratidae, , , , Graphoceratidae, , Erycitidae, and with the new Paradumortieria elmii and Pleydellia (P.?) ruttneri. The fauna represents the Late , Late , , , and Early . Palaeobiogeographically, it is closely related to the Northwest European (Subboreal) Province, and exhibits only minor relations with the Mediterranean (Tethyan) Province.

Key words: , biostratigraphy, palaeobiogeography, Jurassic, Shemshak Group, Alborz Mountains, Iran. Kazem Seyed−Emami [[email protected]] and Ali Shekarifard, School of Mining Engineering, University College of En− gineering. University of , P.O. Box 11365−4563, Tehran, Iran; Franz T. Fürsich [[email protected]−erlangen.de] and Markus Wilmsen [[email protected]−erlangen.de], Geozentrum Nordbayern der Universität Erlangen−Nürnberg, Fachgruppe PaläoUmwelt, Loewenichstraße 28, D−91054 Erlangen, ; Mahmoud R. Majidifard, Geological Survey of Iran [[email protected]], Box 131851−1494, Tehran, Iran.

Introduction Institutional abbreviation.—BSPG, Bayerische Staatssamm− lung für Paläontologie und Geologie, Munich, Germany. All The Shemshak Group (Assereto 1966; Fürsich et al. in press) fossil material described in this paper belong to this collection is a thick siliciclastic succession, widely distributed across and institutional abbreviations are skipped (only specimen central and northern Iran (Fig. 1), the so−called Iran Plate. numbers are provided). The nature of this succession, with immense thicknesses up Other abbreviations.—D, diameter in mm; H, whorl height as to 4,000 m and rapid lateral and vertical changes, indicates % of diameter; U, umbilical width as % of diameter; W, whorl sedimentation in several foreland basins in front of tectoni− width as % of diameter. cally active, uplifted areas of the Cimmerian mountain belt to the north, created by Late movements (the Early Cimmerian Orogenic Event; e.g., Seyed−Emami 2003). The age of the Shemshak Group ranges from Late Triassic to Geological setting Early Bajocian, and sedimentary environments comprise deep to shallow marine shelf, deltas, paralic swamps, lakes In the area of Shahmirzad, 25 km north of Semnan, the and meandering as well as braided rivers (Vollmer 1987; Shemshak Group, with a thickness of up to 2,000 m, is widely Repin 1987; Seyed−Emami et al. 2001, 2005, 2006; distributed. It rests with erosional unconformity on Lower Seyed−Emami 2003; Fürsich et al. 2005; Fürsich et al. in and Middle Triassic limestones and dolomites of the Elikah press). Besides several short−lived marine ingressions in the Formation and is succeeded, apparently disconformably, by Norian, Late Sinemurian, and Late Pliensbachian (Dome− the marls and limestones of the Middle Jurassic Dalichai rian), the most conspicuous and long−lasting transgression Formation (Nabavi and Seyed−Emami 1977). The described within the Shemshak Group occurred during the Toarcian ammonites come from three stratigraphic sections east and and Aalenian, well documented by marine faunas (ammo− southeast of the small town Shahmirzad. Section 1 (Fig. 2) is nites) practically everywhere in the Alborz Range and cen− situated about 1.5 km east of Shahmirzad, north of the asphalt tral Iran (Seyed−Emami 1988; Fürsich et al. 2005). road to Sari (N 35°47’15’’, E 35°20’07’’). Here only the

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Fig. 1. Distribution of the Shemshak Group in the central and eastern Alborz, northern Iran. 1: Position of the Shahmirzad and Kuhe Bashm−e−Dehsufian sections; 2: Position of the Sharif Abad section. lower part of the Shemshak Group is exposed. The upper part ally coincide with transgressive episodes and tectonically rela− of the formation (Fig. 2) was studied at the Kuhe Bashm− tively quiet intervals with little siliciclastic input. These inter− e−Dehsufian pass (Kuhe Bashm), about 14 km further to the vals are often characterized by calcareous sandstones or silty− east, south of the road to Sari (N 35°49’35’’, E 53°25’09’’). sandy limestone intercalations, which are otherwise very sub− The third section (Sharif−Abad; Fig. 3) is situated about ordinate constituents within the predominantly siliciclastic 18 km NNE of Semnan, in a south−north trending valley ca rocks of the Shemshak Group. Taking into consideration the 2 km west of the classic section of Diktash (N 35°42’59’’, great thickness of the Shemshak Group (2,000 m and more) E53°26’01’’). Here again, only the upper part of the forma− and the discontinuous occurrence and scarcity of the fossils, it tion has been studied. was not possible to obtain a continuous, bed by bed collection of the fauna. Previous investigations.—Marine fossils from the Shemshak For a better characterization of the ammonite fauna from Group of the classical area north of Semnan (Diktash) were the Shemshak Group of the Shahmirzad area, also taxa from collected and recorded for the first time by Stahl (1897, 1911). earlier studies and collections by Nabavi and Seyed−Emami The few ammonites of this collection have been studied by (1977), Seyed−Emami and Nabavi (1985), Hosseinzadeh Pompeckj (1897) and Fischer (1914, 1915) and later were re− (2003), and Seyed−Emami and Hosseinzadeh (2006) have vised by Seyed−Emami (1967). More detailed stratigraphic been included in Table 1 and in the discussion. and palaeontological studies on the Shemshak Group of the Due the close relationship of the described fauna with that Shahmirzad area have been carried out by Nabavi and Seyed− of Northwestern Europe, the biozonation follows the stan− Emami (1977), Seyed−Emami and Nabavi (1985) Seyed− dard Northwest European ammonite zonation proposed by Emami (1985, 1987), Nabavi (1987), Repin (1987), Hossein− Dean et al. (1961) and Cariou and Hantzpergue (1997). zadeh (2003), and Seyed−Emami and Hosseinzadeh (2006). Level I (Shahmirzad) Ammonite levels and biostratigraphy.—The described am− Echioceras raricostatum Zone, Late Sinemurian. monite faunas are usually concentrated in certain succeeding Most ammonites are external moulds of small and juvenile levels of the three measured sections at Shahmirzad, Kuhe forms, scattered on bedding planes of several successive, Bashm, and Sharif−Abad (Figs. 2, 3). Each ammonite level very hard, bioclastic sandstones. consists of a single bed or of several beds, a few decimetres to The nearly monospecific fauna consists of Paltechioceras several metres or more in thickness. Between the levels in cf. oosteri. The Early Sinemurian ammonites, described ear− which ammonites are concentrated, there are many metres, or lier by Nabavi and Seyed−Emami (1977) from the same local− even tens of metres, of barren strata. The ammonite levels usu− ity, probably come from the same level. SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 239

Table 1. Stratigraphic distribution and localities of the ammonite taxa from the Shemshak Group of the Shahmirzad area. Listed are all taxa from the present contribution (marked with *) and from previous publications (Nabavi and Seyed−Emami 1977; Seyed−Emami and Nabavi 1985; Seyed−Emami 1987; Seyed−Emami and Hosseinzadeh 2006).

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This is the first record of the Late Sinemurian in Iran. The ammonites probably are evidence of the first marine ingres− sion within the Jurassic part of the Shemshak Group. Palaeo− biogeographically, Paltechioceras oosteri is a rather pande− mic taxon, being known also from Europe (Schlatter 1991; Blau 1998) and North and South America (Hillebrandt 2002). Level II (Shahmirzad); level A (Sharif−Abad) margaritatus Zone, Late Pliensbachian. This level consists of several layers of reworked, hard calcare− ous sandstone concretions in a matrix of fine−grained sand− stone. The scarce fauna comprises, besides large belemnites and bivalves, the following ammonites: Cymbites (Metacym− bites?) fuersichi, Amaltheus cf. stokesi, A. subnodosus, A. margaritatus, Oregonites cf. imlayi, Protogrammoceras (P.) cf. celebratum, P. (Matteiceras)cf.nitescens. Cymbites and Protogrammeras come from the lowest bed, below the beds with Amaltheus. This is the first record of these genera from Iran. So far only a few occurrences of Amaltheus have been re− corded from Shahmirzad (Nabavi and Seyed−Emami 1977), some localities in Central Alborz (Lorenz 1964; Allenbach 1966; Dedual 1967; Pourmotamed and Motamed 1976; Repin 1987), and from a few sites in southwestern Alborz (at Zanjan and Maragheh; KSE personal observations). Until now Amal− theus and the above mentioned taxa have not been recorded from the Shemshak Group of Central Iran. Palaeobiogeographically, Amaltheidae are typical Boreal taxa, being restricted to the northern part of the northern hemi− sphere (Dagis 1976; Meister 1988; Dommergues et al. 1997, 2005; Meister and Stampfli 2000; Smith et al. 2001). Also, Cymbitidae are more or less northern elements being recorded from Europe and North America (e.g., Seyed−Emami and Hosseinzadeh 2006). In contrast, (Protogram− moceras and Matteiceras) are originally Tethyan elements, being widely distributed in circum−Mediterranean areas, but are also known from Northwestern Europe and North America (e.g., Smith and Tipper 1996). Level III (Kuhe Bashm); level B and level C (Sharif−Abad) Dactylioceras tenuicostatum Zone, Early Toarcian. At Kuhe Bashm the ammonites (Dactylioceras [D.] sp., D. [Orthodactylites] aff. semicelatum, D. [O.] cf. tenuicosta− tum, Dactylioceratidae gen. et sp. nov.?) occur in several metres of very hard, well−bedded, greyish−blue sandstone. At Sharif−Abad the ammonites come from level B (D. [Eodact− llites] pseudocommune) and level C (D. [E.]cf. commune, D. [O.] cf. semicelatum), separated from each other by about 12 m of section. The earliest Toarcian in northwest European as well in Mediterranean areas is characterized by the disruption of the Late Pliensbachian Tethyan−Boreal provinciality and the homogeneization of the ammonoid faunas of both provinces,

which lasts until the Bajocian (Macchioni and Cecca 2002). ® Fig. 2. Middle part of the Shemshak Group in the Shahmirzad area, com− bined from the Shahmirzad section (left column) and the Kuhe Bashm−e− Dehsufian section (right two columns). For key see Fig. 3. Fig. 3. Upper part of the Shemshak Group at Sharif−Abad.

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Besides, the Early Toarcian Dactylioceras tenuicostatum Zone The Phlyseogrammoceras dispansum ( is characterized, both in Tethyan and in northwest European ar− speciosum) Zone, which is characterized in Europe by the eas, by the explosion of Dactylioceratidae (Elmi et al. 1997; explosion of Hammatoceras (Elmietal.1997:32),could Page 2004). So far, the Early Toarcian Oceanic Anoxic Event not be proven with certainty. The absence of taxa indicative and the overall extinction and drop in diversity of the ammo− of this zone reflects ecological parameters or insufficient noids (Macchioni and Cecca 2002) could not be recognized in collecting rather than than non−deposition. the Alborz Mountains, because of the scarcity and discontinu− ous dispersal of the fauna and the great thickness of the strata. Level VI (Kuhe Bashm) Dactylioceratidae have been reported sporadically from Pleydella aalensis Zone, Late Toarcian. several sites in the Alborz Mountains (Repin 1987, 2000). In Lithologically, level VI is the continuation of the strata of Central Iran only few occurrences are known from the re− level V. In the lower part there are still some . gions of Kerman (Seyed−Emami 1967) and the northern Lut But higher up, the ammonite fauna consists nearly exclu− (Seyed−Emami et al. 2004). The few specimens of Dactylio− sively of a rich and diverse fauna of Pleydellia, being com− ceras do not allow to draw any significant palaeobiogeo− monly concentrated, similarly to level V, in head−sized con− graphic conclusions. cretions: Pleydellia (P.) mactra, P. (P.) subcompta, P. (P.) Level D (Sharif−Abad) celtica, P. (P.) fluens, P. (P.) aalensis, P. (P.) buckmani, P. bifrons/Haugia variabilis Zone, Middle Toarcian. (P.?) ruttneri, P. (P.?) arkelli, P. (Walkericeras) lotharin− Only a single specimen of Catacoeloceras aff. raquinianum gica, P. (Cotteswoldia) fuselieri, and P. (C.) bifax. was found at this level. Dumortierinae comprise more than 50% of the total fauna Middle Toarcian Hildoceatinae have been recorded from and are closely related to those from northwestern Europe. Ac− few sites in the central and eastern Alborz Mountains (Repin cording to Macchioni and Cecca (2002) all Toarcian Ammo− 1987; Seyed−Emami et al. 2005). There is no reliable record nitina derive from Tethyan ancestors, which belong to the from Central Iran. Tethyan family Hildoceratidae. Level IV (Kuhe Bashm) Level VII (Kuhe Bashm); level F (Sharif−Abad) thouarsense Zone, Pseudogrammoceras fal− Leioceras opalinum Zone (Leioceras opalinum Subzone), laciosum Subzone, Late Toarcian. Early Aalenian. The nearly monospecific fauna comes from a 10 m thick pack− The level consists of sandy marl with intercalations of sandy age of silty marl with intercalations of sandy limestones. It limestones containing large bivalves, gastropods, and belem− consists of Pseudogrammoceras fallaciosum and Podagro− nites. Besides few specimens of finer ribbed Leioceratinae sites latescens. Pseudogrammoceras fallaciosum is the most (Leioceras opalinum) the level is characterized by the sud− constant and widely distributed taxon in the Shemshak Group den appearance and dominance of partly new taxa of Ham− of North and Central Iran, so that a Pseudogrammoceras matoceratinae: alleoni, B. guliense, B. iranica, B. fallaciosum Horizon can be established. alborzensis, B. shahmirzadense, Erycites aff. sphaeroco− Level V (Kuhe Bashm); Level E (Sharif−Abad) nicus. This level distinctly overlies the beds with Pleydellia Dumortieria pseudoradiosa/Pleydella aalensis Zone, Late and underlies the beds with more coarsely ribbed Leio− Toarcian. ceratinae of the Leioceras comptum group. The levels are represented by silty shales and marls with in− Hammatoceratinae are rather rare elements in the Shem− tercalations of lenticular concretionary limestones with large shak Group of the Alborz Mountains, but are fairly common bivalves, gastropods, and belemnites. The relatively rich am− at Kuhe Bashm (about 10% of the ammonite fauna) and in monite fauna consists predominantly of a variety of Dumor− the age−equivalent Badamu Formation of southeastern Cen− tierinae, being often concentrated within head−sized calcare− tral Iran (Kerman−Ravar region; e.g., Seyed−Emami 1967). ous concretions: Dumortieria levesquei, D. excentricostata, D. aequicostata, D. bleicheri, D. brancoi, D. radians, D. Level VIII (Kuhe Bashm) gundershofensis, D. radiosa, D. moorei, Paradumortieria Leioceras opalinum Zone, Leioceras comptum Subzone, Early rustica, P. explanata, P. semnanensis, P. schaireri, P. elmii, Aalenian. and Hammatoceras aff. tipperi. The great number of micro− At this level coarsely ribbed Leioceratinae of the Leioceras conchs (Paradumortieria) is noteworthy. comptum/L. crassicostatum group (Leioceras comptum) occur. Dumortieria appears clearly below the beds with Pley− The level contains the last calcareous beds, which first began dellia, but continues higher up into the lower beds with Pley− to appear at level IV to form a package of about 120 m of dellia. Neither in the Alborz region nor in Central Iran such a marly silt with limestone intercalations, approximately in the richness and diversity of Dumortierinae exist. The total ab− middle part of the section at Kuhe Bashm (Fig. 2). These strata sence of Catulloceras, and the scarcity of Hammatoceratinae are characterized by a relatively rich and diverse ammonite is remarkable. These are common elements in strata of the fauna, as a result of favourable ecological conditions, environ− same age in northwestern Europe as well as in the Tethys re− mental stability, and a low rate of sedimentation. The greater gion (Elmi et al. 1997). part of the fauna comes from this succession. SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 243

Level IX (Kuhe Bashm); level G (Sharif−Abad) Paltechioceras cf. oosteri (Dumortier, 1867) Otoceras concavum Zone, Late Aalenian. Fig. 4F. The few ammonites occurring at this level are Graphoceras 1867 cf. Ammonites oosteri; Dumortier 1867: 164, pl. 30: 3, 4. (G.) concavum, G. (G.) decorum, G. (Ludwigella) cornu, G. 1977 Arnioceras mendax rariplicata Fucini; Nabavi and Seyed−Emami (L.) cf. rudis, and Acardia aff. diadematoides. 1977: 80, fig. 9 (2, 3). At Kuhe Bashm, above the last limestone bed of level VIII, 1991 cf. Paltechioceras cf. oosteri (Dumortier); Schlatter 1991: 44, pl. follows several hundred metres thick package of dark, monot− 5: 8–11; text−fig. 29. 1998 cf. Paltechioceras oosteri (Dumortier, 1867); Blau 1998: 213, pl. onous, fine−grained siliciclastics in which fossils are extre− 10: 14, 17, 19; pl. 14: 2. mely rare. At Sharif−Abad, this unit comprises only 120 m. 2002 cf. Paltechioceras oosteri (Dumortier, 1867); Hillebrandt 2002: The few ammonites (Graphoceratinae) mostly come from 107, pl. 11: 14–21. concretions in the lower third of the succession. The absence Material.—One external mould (050510−2) and several ju− of Middle Aalenian (Ludwigia murchisonae Zone) ammonites venile specimens from Shahmirzad. is for sure related to the scarcity of the fauna due to the high rate of sedimentation, unfavourable ecological conditions (a Dimensions (in mm) dysoxic to anoxic environment), and to preservational condi− Specimen D U H W ribs/whorl tions, lasting until the end of the Aalenian and the beginning of 050510−2 27 ~59 24 – 36 the Bajocian (Fürsich et al. 2005). 69−N−183b 34 58 26 26 36 In contrast to North Iran, Middle–Late Aalenian am− Description.—The figured specimen is extremely evolute, monites are fairly well known from the Badamu Formation tricarinate−bisulcate, with a nearly quadrate whorl cross−sec− of east−central Iran (Seyed−Emami 1967). tion. Ribs are strong, sharp and radiate. At the ventrolateral edge the ribs thicken slightly, bend forward and die out near Level G (Sharif−Abad) the ventral grooves. In a smaller specimen (050510−3/1) the Waagenia propinquans/ humphriesianum suture line is visible. It is relatively simple with minor inden− Zone, Early Bajocian. tations. Several metres of sandy limestones with large bivalves (e.g., Discussion.—With respect to the number and coarseness of Plagiostoma), belemnites, and only a single fragment of ribs, which slightly thicken towards the venter, as well as in Stephanoceratidae (Stemmatoceras? sp.). This is the first re− dimensions our specimens are closely comparable with P. cord of Early Bajocian ammonites from the Shemshak Group oosteri, especially the specimens figured by Schlatter (1991: of North Iran. Contrary to the Alborz area, Early Bajocian pl. 5: 8) and Blau (1998: pl. 10: 4). and Stephanoceratidae are well represented in Previous records of Vermiceras and Arnioceras (Nabavi east−central Iran (Seyed−Emami 1967, 1971, 1988; Seyed− and Seyed−Emami 1977) from the same locality and proba− Emami et al. 1993, 2004). bly from the same level, are most likely misidentifications and also belong to the genus Paltechioceras. Similarly, Ver− miceras scylla (Reynès, 1879) in Nabavi and Seyed−Emami Systematic palaeontology (1977: 80, fig. 9/1) is probably a Paltechioceras. Except for the venter, which does not seem to be tricarinate, the latter Order Ammonitida Zittel, 1884 closely resembles P. aplanatum (Hyatt, 1889) of Schlatter Suborder Phylloceratina Arkell, 1950 (1991: pl. 7: 2). Superfamily Phylloceratoidea Zittel, 1884 Stratigraphic and geographic range.—Shahmirzad, level I. Family Phylloceratidae Zittel, 1884 Paltechioceras oosteri is widely distributed in the Late Sine− Genus Phylloceras Suess, 1865 murian of Europe, being also recorded from North and South America (Hillebrandt 2002). Blau (1998: 234) recorded P. Phylloceras sp. oosteri from the Paltechioceras aplanatum Subzone of the Fig. 4A. Echioceras raricostatum Zone, Upper Sinemurian (Lotharin− Material.—A single inner whorl from Sharif−Abad (050512− gian). This is the first record of Paltechioceras from Iran. 11/13). Stratigraphic and geographic range.—The single inner whorl Superfamily Hyatt, 1867 was collected from the scree together with a mixed fauna from Family Amaltheidae Hyatt, 1867 the Lower Aalenian. Genus Amaltheus de Monfort, 1808 Suborder Hyatt, 1889 Amaltheus cf. stokesi (J. Sowerby, 1818) Fig. 4B. Superfamily Psiloceratoidea Hyatt, 1867 1818 cf. Ammonites Stokesi; J. Sowerby 1818: 205, pl. 190. Family Echioceratidae Buckman, 1913 1977 Amaltheus stokesi (Sowerby); Nabavi and Seyed−Emami 1977: Genus Paltechioceras Buckman, 1927 81, fig. 9 (5, 6 only).

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1998 cf. Amaltheus stokesi (Sowerby, 1818); Géczy and Meister 1998: Hashem (northeast of Tehran, Central Alborz) and more 102, pl. 6: 10 (with synonymy). than 10 poorly preserved inner whorls from Shahmirzad 2003 Amaltheus stokesi (Sowerby, 1818); Hosseinzadeh 2003: 61, pl. (050514−6) and Sharif−Abad (050512−5). Specimens H−233 1: 17, 18. and 90−SE−1 come from earlier collections made by Moha− Material.—Several poorly preserved inner whorls from Shah− mmad Hosseinzadeh from Shahmirzad and K.S.−E. from mirzad (050514−6). Emam−Zadeh Hashem Pass in Central Alborz. Description and discussion.—Among the small and poorly Dimensions (in mm) preserved amaltheids from Shahmirzad there are several Specimen D U H W specimens which may be assigned to A. stokesi. The figured 050514−6/3 16 31 44 – specimen (050514−6/6) is a relatively coarsely ribbed Amal− 050514−6/2 24 31 42 ~25 theus. The ribs bifurcate near the venter and cross it as chev− 050514−6/5 31 38 37 ~23 (evolute specimen) rons. The passage from the flank to the venter is gradual, and H−233 38 34 41 ~21 (finely ribbed specimen) 90−SE−1 44 23 ~48 – the keel is not as prominent as that of A. margaritatus. Juve− nile specimens of A. stokesi and A. margaritatus cannot be Description.—Specimen 90−SE−1 (Fig. 4G) is a flat, oxy− distinguished from each other with certainty, which has been cone and relatively involute Amaltheus, with a rather promi− already mentioned by Howarth (1958: 5). nent and fairly finely crenulated keel. Ribs are medium− coarse and slightly sigmoidal. Close to the venter the ribs Stratigraphic and geographic range.—Shahmirzad, level II. curve forward and almost fade before reaching the keel. A. stokesi is widely distributed in the boreal regions of north− west Europe, northwest America, Siberia and Caucasus, oc− Discussion.—The specimens from Shahmirzad are small in− curring in the Amaltheus stokesi Subzone of the Amaltheus ner whorls, with a varying degree of involution and coarseness margaritatus Zone, Late Pliensbachian (Smith and Tipper of the ribs. Specimen H−233 (Fig. 4T) is very finely ribbed, 1996: 51). looking much like A. depressus Simpson, 1843, stadium com− pressum Quenstedt in Frentzen (1937: pl. 2: 4). The latter has Amaltheus margaritatus de Montfort, 1808 been regarded as a synonym of A. margaritatus by Howarth Fig. 4C, D, G, T. (1958: 140). Nevertheless, the juvenile, poorly preserved spe− 1808 Amaltheus margaritatus; de Montfort 1808: 91, fig. 90. cimens from Shahmirzad can be placed, with caution, within 1958 Amaltheus margaritatus de Montfort; Howarth 1958: 13, pl. 3: the range of variation of A. margaritatus of Meister (1988). 4–6; text−figs. 8, 9 (with synonymy). On a slab with A. margaritatus (90−SE−1) there is a fragment 1976 Amaltheus margaritatus de Montfort; Pourmotamed and Mota− of Amauroceras sp., looking much like A. ferruginum (Simp− med 1976: 106, fig. 3. son, 1843) of Meister (1986: pl. 20: 7). The genus Amauro− 1977 Amaltheus stokesi (Sowerby); Nabavi and Seyed−Emami 1977: ceras has been considered to be the microconch form to 81, fig. 9 (4, 5 only). 1986 Amaltheus margaritatus (de Montfort 1808); Meister 1986: 95, Amaltheus by Meister (1986: 125). pl. 20: 9; pl. 22: 1; pl. 23: 6 (with synonymy). Stratigraphic and geographic range.—Shahmirzad, level II; 1998 Amaltheus margaritatus de Montfort, 1808; Géczy and Meister Sharif−Abad, level A; Amaltheus margaritatus Zone, Late 1998: 103 (with synonymy). Pliensbachian (Domerian). Amaltheids are typical Boreal Material.—One specimen from Gardaneh−e−Emamzaheh− and “Euroboreal” taxa (Dagis 1976; Meister 1988; Meister

Fig. 4. Upper Sinemurian to Lower Aalenian ammonoids from the Shemshak Group. A. Phylloceras sp., Sharif−Abad, 050512−11/13, Lower Aalenian; aper− ® tural (A1) and lateral (A2)views.B. Amaltheus cf. stockesi (J. Sowerby, 1818), Shahmirzad, 050514−6/6, Amaltheus margaritatus Zone, Upper Pliensbachian; lateral (B1) and ventral (B2)views.C, D, G, T. Amaltheus margaritatus de Montfort, 1808, A. margaritatus Zone, Upper Pliensbachian. C. Shahmirzad, 050514−6/2, lateral view. D. Shahmirzad, 050514−6/5; lateral (D1) and ventral (D2)views.G. Gardaneh−e−Emmamzadeh−Hashem, Central Alborz, 80−SE−1, lateral view. T. Shahmirzad, H−233; lateral (T1) and ventral (T2)views.E. Amaltheus subnodosus (Young and Bird, 1828), Shahmirzad, 050514−6/1, A. subnodosus Subzone, A. margaritatus Zone; lateral (E1) and apertural (E2)views.F. Paltechioceras cf. oosteri (Dumortier, 1867), Shahmirzad, 050510−2, Echioceras raricostatum Zone, Upper Sinemurian (plaster cast), lateral view. H. Protogrammoceras (Protogrammoceras)cf.celebratum (Fucini, 1900), Shahmirzad, 050514−6/12, A. margaritatus Zone, Upper Pliensbachian; lateral (H1) and ventral (H2)views.I, M. Dactylioceras (Orthodactylites) aff. semicelatum (Simpson, 1843), Dactylioceras tenuicostatum Zone, Lower Toarcian. I. Sharif−Abad, 050512−7/1; lateral (I1) and ventral (I2)views. M. Sharif−Abad, 050512−7/4; lateral (M1) and ventral (M2)views..J. Oregonites sp. cf. O. imlayi Wiedenmayer, 1980, Shahmirzad, 050514−6/10, Upper Pliensbachian; lateral (J1) and ventral (J2)views.K. Protogrammoceras (Matteiceras)cf.nitescens (Young and Bird, 1828), Shahmirzad, 050514−6/10, A. margaritatus Zone, Upper Pliensbachian; lateral (K1) and ventral (K2)views.L. Dactylioceras (Eodactylites?) pseudocommune Fucini, 1935, Sharif−Abad, 050512−6/1, D. tenuicostatum Zone, Lower Toarcian; lateral (L1) and ventral (L2)views.N, R. Dactylioceras (Orthodactylites)sp.,cf.D. (O.) tenuicostatum (Young and Bird, 1822), Kuhe Bashm−e−Dehsufian, Lower Toarcian. N. 80−SE−5 (crushed specimen), lateral view. R. 80−SE−19 (plaster cast), lateral view. O. Dactylioceratidae indet., Kuhe Bashm−e−Dehsufian, H−204, D. tenuicostatum Zone, Lower Toarcian; lateral (O1) and apertural (O2)views.P. Dactylioceras (Eodactylites?) cf. pseudocommune Fucini, 1935, Sharif−Abad, 050512−7/2, Arnioceras semicostatum Zone, Lower Toarcian; lateral (P1) and ventral (P2) views. Q. Dactylioceras (Dactylioceras) sp., Kuhe Bashm−e−Dehsufian, 80−SE−16, ?Middle Toarcian; lateral (Q1) and apertural (Q2)views.S. Para− dumortieria schaireri (Seyed−Emami, 1985) [m], Kuhe Bashm−e−Dehsufian, 050511−3/5, Pleydella aalensis Zone, Upper Toarcian; lateral (S1,S2) and ventral (S3)views.U. Podagrosites latescens (Simpson, 1843), Kuhe Bashm−e−Dehsufian, 050510−16/3, Pseudogrammoceras fallaciosum Subzone, Grammoceras thouarsense Zone, Upper Toarcian; lateral (U1) and ventral (U2)views.V. Dumortieria radiosa (Seebach, 1864), Kuhe Bashm−e−Dehsufian, 050511−3/7, Pleydella aalensis Zone, Upper Toarcian, lateral view (impression of Fig. 5J1). W. Dumortieria moorei (Lycett, 1857), Kuhe Bashm−e−Dehsufian, 050511−3, Pleydella aalensis Zone, Upper Toarcian, lateral view (impression). Arrows indicate onset of body chamber; m = microconch. SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 245

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http://app.pan.pl/acta53/app53−237.pdf 246 ACTA PALAEONTOLOGICA POLONICA 53 (2), 2008 and Stampfli 2000; Smith et al. 2001), which occur only spo− Elsewhere, D. commune occurs in the Middle Toarcian (D. radically in northern Iran (Nabavi and Seyed−Emami 1977; commune Subzone). Seyed−Emami 1988). So far, this is the southernmost occur− rence of the family within the northern hemisphere (north− Subgenus Eodactylites Schmidt−Effing, 1972 western Tethys). Dactylioceras (Eodactylites?) pseudocommune Amaltheus subnodosus (Young and Bird, 1828) Fucini, 1935 Fig. 4E. Fig. 4L. 1828 Ammonites subnodosus; Young and Bird 1828: 258, pl. 13: 3. 1935 Dactylioceras pseudocommune sp. nov.; Fucini 1935: 86, pl. 9: 1958 Amaltheus subnodosus (Young and Bird); Howarth 1958: 8, pl. 2: 1–3. 11–18; text−fig. 6 (with synonymy). 1966 Dactylioceras pseudocommune Fucini 1935; Fischer 1966: 26, pl. Material.—One fairly well preserved specimen with parts of 1: 5; pl. 4: 3, 6. the body whorl (050514−6/1) and two fragments (050514− 1972 Dactylioceras (Eodactylites) pseudocommune Fucini, 1935; Schmidt−Effing 1972: 91, pl. 3: 1a–c; pl. 18: 7; text−fig. 15. 6/4, 050514−6/9) from Shahmirzad. 1973 Dactylioceras (Dactylioceras) pseudocommune Fucini; Howarth Dimensions (in mm) 1973: 253, pl. 1: 1 (with synonymy). Specimen D U H W ribs/whorl 1994 Eodactylites pseudocommunis (Fucini); Faraoni et al. 1994: pl. 3: 050514−6/1 23 37 39 ~35 15 (end of phragmocone) 1; pl. 4: 1–3, 5. 31 38 35 ~24 18 (on the body whorl) Material.—Two specimens from Sharif−Abad (050512−6/1, Description.—The figured specimen is a rather small, evolute 050506/2). and coarsely ribbed Amaltheus with elliptical whorl cross−sec− Dimensions (in mm) tion and a prominent crenulated keel. On the inner part of the Specimen D U H W flank ribs are strong, radiate−straight, with tubercles about the 050512−6/1 79 54 26 23 mid−flank. Near the venter, the ribs bend forward, become Description.—The figured specimen is a very evolute fainter, and bifurcate indistinctly. On the body chamber, the Dactylioceras, with nearly parallel, flat flanks and an arched ribbing is slightly denser and less coarse and the tubercles venter. The whorl cross−section is rectangular to ovate. On gradually fade. the last preserved whorl the ribs are coarse, rectiradiate, Discussion.—The described specimen matches well the neo− rather sharp, and widely spaced. Most of the ribs bifurcate at type of A. subnodosus, designated by Howarth (1958: pl. 2: the ventrolateral edge, but a few ribs are simple. There are no 11). Another very similar specimen is A. margaritatus forme distinct tubercles at the point of bifurcation. On the crushed subnodosus of Meister (1988: pl. 1: 6). inner whorl the ribbing is relatively fine and dense. Stratigraphic and geographic range.—Shahmirzad, level II. Discussion.—Our specimen closely matches the one figured A. subnodosus is reported to occur in the lower part of the by Fucini (1935: pl. 9: 1), which has been designated as Amaltheus margaritatus Zone (A. subnodosus Subzone). lectotype by Schmidt−Effing (1972: 91). The characteristic gable−shaped venter, being discussed by Fischer (1966) and Family Dactylioceratidae Hyatt, 1867 Schmidt−Effing (1972), cannot be observed in our specimen, Genus Dactylioceras Hyatt, 1867 partly because of erosion. Subgenus Dactylioceras Hyatt, 1867 Stratigraphic and geographic range.—Dactylioceras (E.) Dactylioceras (Dactylioceras) sp. pseudocommune is largely a Mediterranean form, known to Fig. 4Q. occur in the Late Pliensbachian (Domerian) or Early Material.—One specimen from earlier collections by K.S.−E. Toarcian (Fucini 1935; Schmidt−Effing 1972; Faraoni et al. from Kuhe Bashm: (80−SE−16). 1994). Howarth (1973) recorded it from the base of the Dactylioceras tenuicostatum Zone. At Sharif−Abad it was Dimensions (in mm) found at level B, above the beds with Amaltheus and below Specimen D U H W the beds with Dactylioceras semicelatum. 80−SE−16 41 48 29 29 Description.—Evolute Dactylioceras with nearly flat flanks, a Dactylioceras (Eodactylites?) cf. pseudocommune quadratic whorl cross−section and a slightly rounded venter. Fucini, 1935 On the last preserved whorl the ribbing is relatively coarse and Fig. 4P. widely spaced. The slightly prorsiradiate primaries bifurcate 1935 cf. Dactylioceras pseudocommune n. sp.; Fucini 1935: 86, pl. 9: ventrolaterally. 1–3. Discussion.—The coarse ribbing and the quadratic whorl Material.—One specimen, partly covered by matrix, from cross−section are similar to the lectotype of D. commune (J. Sharif−Abad (050512−7/2). Sowerby, 1815) refigured by Dean et al. (1961: pl. 72: 5a, b). Dimensions (in mm) Stratigraphic and geographic range.—The precise stratigra− Specimen D U H W phic position of the loosely collected specimen is not known. 050512−7/2 36 50 32 28 SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 247

Description.—Evolute Dactylioceratidae with flat flanks, a figured by Howarth (1973: 258, pl. 5: 1, 2; pl. 6: 2, 3) and nearly rectangular whorl cross−section and a rounded venter. Howarth (1980: 650, pl. 82: 1–10, 13, 14). The ribbing is coarse, with straight and slightly prorsiradiate Stratigraphic and geographic range.— Kuhe Bashm, level primaries, bifurcating near the venter, apparently without III. D. (O.) tenuicostatum has been recorded from the Lower any tubercles. Toarcian Dactylioceras tenuicostatum Zone. Discussion.—The coarse ribbing, flat sides, and rectangular Dactylioceratidae indet. whorl cross−section are very similar to D. (E.) pseudo− commune Fucini, 1935. Fig. 4O. Stratigraphic and geographic range.—The specimen was Material.—One fragmentary phragmocone collected by found together with D. (O.) semicelatum from the Early Hosseinzadeh (2003) from Kuhe Bashm (H−204). Toarcian Dactylioceras semicelatum Zone (Sharif−Abad, Description.—At a diameter of 20 mm the specimen is rela− level C). tively evolute with an ovate whorl cross−section and flanks converging slightly towards the arched venter. The last pre− Subgenus Orthodactylites Buckman, 1926 served whorl becomes distinctly involute with a deep umbili− Dactylioceras (Orthodactylites) aff. semicelatum cus and a vertical umbilical wall. Moreover, the whorls be− (Simpson, 1843) come considerably wider (W/H ratio = 92%), with flanks converging strongly towards the venter, resulting in a trian− Fig. 4I, M. gular−ovate whorl cross−section. The ribbing is extremely 1843 aff. Ammonites semicelatus; Simpson 1843: 20. fine, dense, and sharp. The slightly prorsiradiate primaries 1972 aff. Dactylioceras (Orthodactylites) semicelatum (Simpson, 1843); (22 per half−whorl at D = 20 mm) bifurcate almost regularly Schmidt−Effing 1972: 95, pl. 4: 1–4; pl. 19: 13; text−figs. 16, 17. 1980 aff. Dactylioceras (Orthodactylites) semicelatum (Simpson); about the mid−flank. The slightly finer secondaries cross the Howarth 1980: 646, pls. 80, 81; pl. 82: 11, 12; text−figs. 2, 3 (with arched venter in a straight line. No tubercles are developed at synonymy). the bifurcation point. 2004 aff. Dactylioceras (Orthodactylites) semicelatum (Simpson 1843); Discussion.—To some extent, the specimen has the appear− Seyed−Emami et al. 2004: 81, pl. 1: 1. ance of a . The narrow umbilicus and the Material.—Three inner whorls from Sharif−Abad (050512− fine ribbing of the last preserved whorl resembles Dactylio− 7/1, 050512−7/3, 050512−7/4) and two specimens from Kuhe ceras (Iranodactylites) ketevanae Repin (2000: 40, pl. 3: 1, Bashm collected earlier on by K.S.−E. (80−SE−18, H−209). 2), from which our specimen differs by its distinct broadness Dimensions (in mm) and a nearly triangular whorl cross−section. A very similar, Specimen D U H W perhaps conspecific specimen is Dactylioceras sp. nov. from 050512−7/1 36 42 31 29 the Shemshak Group of the Lut Block, East Central Iran 050512−7/4 40 42 30 31 (Seyed−Emami et al. 2004: 81, pl. 1: 3a, b). However, the lat− Description.—Moderately evolute Dactylioceras with an ter has a finer and denser ribbing. ovate, slightly higher than wide whorl cross−section, which Stratigraphic and geographic range.—Repin (2000: 41) re− converges a little towards the rounded venter. The ribs are corded D. (I.) ketevanae from the Zone. slightly prorsiradiate, sharp, dense, relatively fine, single or The specimen from the Lut Block comes from the Lower bifurcating on the outer part of the flank. Ventrolateral tuber− Toarcian (Seyed−Emami et al. 2004). Hosseinzadeh (2003: cles are not developed at any stage. 67) found the described specimen, together with D. (O.) Discussion.—Except for the somewhat narrower umbilicus, semicelatum, in the Dactylioceras tenuicostatum Zone of the our specimens fits well within the range of variation of the Early Toarcian. species given by Howarth (1980: pl. 81: 1, 2). Stratigraphic and geographic range.—Kuhe Bashm, level III; Genus Catacoeloceras Buckman, 1923 Sharif−Abad, level C. D. (O.) semicelatus is widely distributed Catacoeloceras aff. raquinianum (d'Orbigny, 1845) in Europe, occurring in the Dactylioceras tenuicostatum Zone Fig. 5O. (?Dactylioceras semicelatum Subzone) of the Early Toarcian. 1845 aff. Ammonites Raquinianum; d'Orbigny 1845: 332, pl. 106: 4, 5 Dactylioceras (Orthodactylites) cf. tenuicostatum (only). 1972 aff. Catacoeloceras raquinianum (d'Orb.); Guex 1972: 640, pl. (Young and Bird, 1822) 11: 6. Fig. 4N, R. 1994 aff. Catacoeloceras raquinianum (d'Orbigny, 1845); Atrops in Material.—Four fragmentary and crushed specimens from Fischer 1994: 94, pl. 33: 2a–c. Kuhe Bashm (050510−13/1, 050513/2, and from earlier col− Material.—One fragmentary impression and a small frag− lections by K.S.−E. (80−SE−5, 80−SE−19). ment from Sharif−Abad (050512−8/2, 0505128/4). Discussion.—The wide umbilicus with extremely fine and Description.—The figured specimen (050512−8/2) is a plaster dense ribs allows the fragmentary specimens to be compared cast of an external mould. It is a depressed and rather evolute with D. (O.) tenuicostatum and allied forms, discussed and member of the Dactylioceratidae with broad venter. The rib−

http://app.pan.pl/acta53/app53−237.pdf 248 ACTA PALAEONTOLOGICA POLONICA 53 (2), 2008 bing consists of relatively strong, prorsiradiate primary ribs, lar genus Fontanelliceras (Fucini, 1931) by more depressed beginning at the umbilical seam. These end ventrolaterally in whorls, a distinctly tricarinate−bisulcate venter and paired ribs. small and sharp tubercles, from where they usually trifurcate Stratigraphic and geographic range.—Shahmirzad, level II. into fine secondary ribs. One or two intercalatory ribs, begin− Oregonites is a very rare taxon, being known so far only from ning at the seam or higher up, are present. the Late Pliensbachian of the Mediterranean area (Wieden− Discussion.—Except for the finer ribbing and the more nu− mayer 1980) and North America (Imlay 1968; Smith and Tip− merous secondaries, our specimens compare well with the per 1996). smaller specimen of d'Orbigny (1845: figs. 4, 5), which has been designated as lectotype by Guex (1972: 640). Subfamily Harpoceratinae Neumayr, 1875 At the same time Schmidt−Effing (1972: 63) designated the larger specimen of d'Orbigny (1845: figs. 1, 2) as lecto− Genus Protogrammoceras Spath, 1913 type. Also Atrops (Fischer 1994: 94) considered the larger of Subgenus Protogrammoceras Spath, 1913 d'Orbigny's specimens (d'Orbigny 1845: fig. 1a, b) as the Protogrammoceras (Protogrammoceras) cf. lectotype of the species. celebratum (Fucini, 1900) Stratigraphic and geographic range.—Sharif−Abad, level D. Fig. 4H. C. raquinianum has been recorded from the Middle Toarcian 1900 cf. Grammoceras celebratum; Fucini 1900: 41, pl. 10: 1, 2. Hildoceras bifrons Haugia variabilis / Zone. 1989 cf. P.(Protogrammoceras) celebratum (Fucini, 1900); Meister 1989: 40, pl. 3: 14, 15; pl. 4: 1 (with synonymy). Superfamily Hildoceratoidea Hyatt, 1867 1997 cf. Protogrammoceras celebratum (Fucini); Dommergues et al. Family Hildoceratidae Hyatt, 1867 in Cariou and Hantzpergue 1997: pl. 8: 3. 1998 cf. Protogrammoceras gr. celebratum (Fucini, 1900); Géczy and Subfamily Arieticeratinae Howarth, 1955 Meister 1998: 108, pl. 12: 7–9; pl. 13: 1–3, 5. Genus Oregonites Wiedenmayer, 1980 Material.—Two fragmentary specimens from Shahmirzad Oregonites cf. imlayi Wiedenmayer, 1980 (050514−6/11, 050514−6/12). Fig. 4J. Description.—The figured specimen (050514−6/12) is a Material.—A fragmentary inner whorl with a small portion planulate and evolute member of the Harpoceratinae with a of the body−whorl, starting at a diameter of ca. 24 mm, from high−ovate acute whorl cross−section and a distinct, high Shahmirzad (050510−9). keel. The ribs are simple, falciform, fine and dense, project− Dimensions (in mm) ing strongly on the venter. Specimen D U H W Discussion.—The strongly falciform and fine ribbing resem− 050510−9 20 ~50 30 42 bles P. celebratum. The specimens therefore is placed, with Description.—The small specimen is evolute, tricarinate− reservation, within the range of variation of the species, as bisulcate with a depressed, broad−elliptical whorl cross−sec− given by Ferretti (2002: 208). tion and a strong keel bordered by rather deep sulci. The Stratigraphic and geographic range.—Shahmirzad, level II. strong and slightly rursiradiate ribs start irregularly paired at P. celebratum is widely distributed within eastern Europe and the umbilical margin. On the venter, the ribs bend forward the Mediterranean, occurring in the Amaltheus stokesi Sub− and fade before reaching the sulci. zone of the Amaltheus margaritatus Zone. In Iran, Proto− Discussion.—The evolute specimen resembles Oregonites grammoceras is a very rare taxon. At Shahmirzad, it was col− imlayi Wiedenmayer, 1980. Oregonites differs from the simi− lected just below the beds with Amaltheus.

Fig. 5. Toarcian ammonoids from the Shemshak Group. A–D, Q. Paradumortieria elmii Seyed−Emami nov. sp. [m], Kuhe Bashm−e−Dehsufian, Pleydella ® aalensis Zone, Upper Toarcian. A. Holotype, 050511−3/1 (full−grown specimen with lappets); lateral (A1) and ventral (A2) views. B. Paratype, 050511−3/6; lateral (B1) and ventral (B2) views. C. 7−21−1; lateral (C1) and ventral (C2) views. D. 14−49 (full−grown specimen with lappets); lateral (D1) and ventral (D2) views. Q. Paratype, 050511−3/2, lateral view. E. Pleydellia (Pleydellia) aalensis (Zieten, 1830), Kuhe Bashm−e−Dehsufian, 050511−6/3, P. aalensis Zone, Upper Toarcian; lateral (E1) and ventral (E2) views. F, G. Pleydellia (Pleydellia) buckmani, Maubeuge, 1947, Kuhe Bashm−e−Dehsufian, P. aalensis Zone, Upper Toarcian. F. 050511−6/2, lateral view. G. 050511−6/13; lateral (G1) and ventral (G2) views. H. Pleydellia (Pleydellia) subcompta (Branco, 1879), Kuhe Bashm−e−Dehsufian, 050511−5/1, P. aalensis Zone, Upper Toarcian, lateral view. I, K. Dumortieria moorei (Lycett, 1857), Kuhe Bashm−e− Dehsufian, P. aalensis Zone, Upper Toarcian. I. 050511−3/4; lateral (I1) and ventral (I2) views. K. 050511−3/5; lateral (K1) and apertural (K2) views. J. Dumortieria radiosa (Seebach, 1864), Kuhe Bashm−e−Dehsufian, 050511−3/3, P. aalensis Zone, Upper Toarcian, lateral view. L, M. Pleydellia (Pleydellia?) ruttneri Seyed−Emami sp. nov. [m], Kuhe Bashm−e−Dehsufian, P. aalensis Zone, Upper Toarcian. L. Paratype, 050511−6/10; lateral (L1) and apertural (L2) views. M. Holotype, 050511−6/9 (complete specimen with lappets); lateral (M1) and ventral (M2) views. N. Pseudogrammoceras fallaciosum (Bayle, 1878), Kuhe Bashm−e−Dehsufian, 050510−16/1, Pseudogrammoceras fallaciosum Subzone, Grammoceras thouarsense Zone, Upper Toarcian; lat− eral (N1,N2) and ventral (N3) views. O. Catacoeloceras aff. raquinianum (d'Orbigny, 1845), Sharif−Abad, 050512−8/4, Hildoceras bifrons/Haugia variabilis Zone, Middle Toarcian (plaster cast), lateral view. P. Pleydellia (Cotteswoldia) bifax Buckman, 1904, Kuhe Bashm−e−Dehsufian, P. aalensis Zone, Upper Toarcian, lateral view. R. Paradumortieria schaireri (Seyed−Emami, 1985) [m], Kuhe Bashm−e−Dehsufian, 050511−3/3, P. aalensis Zone, Upper Toarcian, lateral view (external mould of Fig. 4S1). Arrows indicate onset of body chamber; m = microconch. SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 249

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Subgenus Matteiceras Wiedenmayer, 1980 2005 Podagrosites latescens (Simpson, 1843); Seyed−Emami et al. Protogrammoceras (Matteiceras) cf. nitescens 2005: 357, figs. 4C, 5A. (Young and Bird, 1828) Material.—One fragmentary inner whorl from Kuhe Bashm (050510−16/3). Fig. 4K. Description and discussion.—See Seyed−Emami et al. (2005). 1828 cf. Ammonites nitescens; Young and Bird 1828: 257. 1992 cf. Protogrammoceras (Matteiceras) nitescens (Young and Bird, Stratigraphic and geographic range.—Kuhe Bashm, level IV. 1828); Howarth 1992: 66, pl. 4: 4–6; pl. 5: 2; text−fig. 12 (with Late Toarcian, Grammoceras thouarsense Zone, Pseudo− synonymy). grammoceras fallaciosum Subzone. Material.—One fully septate inner whorl from Shahmirzad (050514−6/10). Family Graphoceratidae Buckman, 1905 Dimensions (in mm) Subfamily Dumortieriinae Maubeuge, 1950 Specimen D U H W Genus Dumortieria Haug, 1885 050514−6/10 26 34 39 ~38 Dumortieria radiosa (Seebach, 1864) Description.—A relatively evolute form with a slightly higher Figs. 4V, 5J. than wide, ovate whorl cross−section. The venter is fairly 1864 Ammonites radiosus; Seebach 1864: 142, pl. 9: 2. broad, with a well−defined keel. The ribs are moderately 2006 Dumortieria radiosa (Seebach, 1864); Seyed−Emami et al. 2006: coarse, simple or indistinctly bifurcating close to the umbili− 265, fig. 5/21. cus. On the inner part of the flank the ribs are prorsiradiate. On Material.—Two specimens from Kuhe Bashm−e−Dehsufian the outer part of the flank the ribs bend backward and become (050511−3/3, 050511−3/7). rursiradiate. Near the venter the ribs become raised and project strongly on the venter but fade before reaching the keel. Description.—See Seyed−Emami and Nabavi (1985: 254) and Seyed−Emami et al. (2006). Discussion.—The described specimen is a fully septate inner whorl. Although incomplete, it shows some resemblance to Stratigraphic and geographic range.—Kuhe Bashm, level V. P. (M.) nitescens, especially to the specimen figured by Late Toarcian, Dumortieria pseudoradiosa/Pleydella aalensis Meister (1989: pl. 3: 12). Compared with the latter, our speci− Zone. men is less evolute and the ribbing less coarse. Dumortieria moorei (Lycett, 1857) Stratigraphic and geographic range.—Shahmirzad, level II. Figs. 4W, 5I, K. In Europe, P. (M.) nitescens is not uncommon in the Amal− 1857 Ammonites Moorei; Lycett 1857: 122, pl. 1: 2. theus stokesi Subzone. In Iran, it has been encountered for 1985 Dumortieria moorei (Lycett); Seyed−Emami and Nabavi 1985: the first time, just below the beds with Amaltheus. 255, fig. 9a, b. 1993 Dumortieria moorei (Lycett, 1857); Seyed−Emami et al. 1993: Subfamily Grammoceratinae Buckman, 1904 16, pl. 1: 2. Genus Pseudogrammoceras Buckman, 1901 Material.—More than ten well−preserved specimens from Kuhe Bashm (050511−3). Pseudogrammoceras fallaciosum (Bayle, 1878) Dimensions (in mm) Fig. 5N. Specimen D U H W 1878 Grammoceras fallaciosum; Bayle 1878: pl. 78: 1, 2. 050511−3/4 42 37 38 22 2005 Pseudogrammoceras fallaciosum (Bayle, 1878); Seyed−Emami 050511−3/8 52 38 35 ~20 et al. 2005: 357, fig. 5B, C (with synonymy). 050511−3/5 59 35 37 – Material.—Over ten well preserved specimens from Kuhe Description and discussion.—See Seyed−Emami and Nabavi Bashm−e−Dehsufian (050510−15/1–050510−15/12, 050510−16/1, (1985: 255). 050510−16/2). Stratigraphic and geographic range.—Kuhe Bashm, level V. Dimensions (in mm) Late Toarcian, Dumortieria pseudoradiosa/Pleydella aalensis Specimen D U H W Zone. 050510−16/1 71 31 41 ~21 (fully septate) Description and discussion.—See Seyed−Emami et al. (2005). Genus Paradumortieria Elmi and Caloo, 1985 Stratigraphic and geographic range.—Kuhe Bashm, level Paradumortieria schaireri (Seyed−Emami, 1985) IV. Late Toarcian Grammoceras thouarsense Zone, Pseudo− Figs. 4S, 5R. grammoceras fallaciosum Subzone. 1985 Dumortieria schaireri Seyed−Emami, 1985; Seyed−Emami and Nabavi 1985: 259, figs. 7a, b, 8a, b. Genus Podagrosites Guex, 1973 Material.—One slightly crushed internal mould (D = 30 mm) Podagrosites latescens (Simpson, 1843) with beginning of the lappet from Kuhe Bashm (050511−3/5). Fig. 4U. Description and discussion.—See Seyed−Emami and Nabavi 1843 Ammonites latescens; Simpson 1843: 54–55. (1985: 259). SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 251

Stratigraphic and geographic range.—Kuhe Bashm, level V. Genus Pleydellia Buckman, 1899 Together with Dumortieria radiosa/moorei in the Late Toar− Subgenus Pleydellia Buckman, 1899 cian Dumortieria pseudoradiosa/Pleydella aalensis Zone. Pleydellia (Pleydellia) subcompta (Branco, 1879) Fig. 5H. Paradumortieria elmii Seyed−Emami sp. nov. 1879 subcomptum; Branco 1879: 90, pl. 5: 3, 3a. Fig. 5A–D, Q. 2004 Pleydellia subcompta (Branco, 1879); Myczyński 2004: 65, fig. 1985 Dumortieria aff. schaireri Seyed−Emami, 1985; Seyed−Emami 25/4. and Nabavi 1985: 260, fig. 6a–c. 2005 Pleydellia (Pleydellia) subcompta (Branco, 1879); Seyed−Emami Type material: The holotype is a complete microconch form with lappet et al. 2005: 360, fig. 6E, J. (050511−3/1; Fig. 5A1,A2). Paratypes: specimens 050511−3/2 and −3/6. Material.—One specimen from Kuhe Bashm (050511−5/1). Hypotype: 14−2−3 (originally figured as Dumortieria aff. schaireri Seyed−Emami by Seyed−Emami and Nabavi 1985: fig. 6a–c). Dimensions (in mm) Specimen D U H W Type horizon: Shemshak Group, Upper Toarcian, Pleydella aalensis 050511−5/1 45 29 41 – Zone, Kuhe Bashm section, level V at 245 m (Fig. 2). Type locality: Kuhe Bashm, 13.5 km east of Shahmirzad, about 25 km Description and discussion.—See Seyed−Emami and Nabavi north of Semnan. (1985: 264) and Seyed−Emami et al. (2005). Derivation of the name: In honour of the Late Prof. Dr. S. Elmi Stratigraphic and geographic range.—Kuhe Bashm, level (1936–2007) VI. Late Toarcian, Pleydella aalensis Zone. Material.—Seven, mostly well−preserved specimens from Pleydellia (Pleydellia) aalensis (Zieten, 1830) the Kuhe Bashm section (050511−3 and earlier collections by Fig. 5E. K.S.−E.: 7−21−1, 14−2−3, 14−49). 1830 Ammonites aalensis; Zieten 1830: pl. 28: 3. Diagnosis.—Small, evolute microconchs with elongated lap− 2004 Pleydellia aalensis (Zieten, 1830); Myczyński 2004: 64, fig. pets and rectangular to high−ovate whorl cross−section. Venter 26/3. tectiform with a distinct keel. Ribbing relatively coarse, 2005 Pleydellia (Pleydellia) aalensis (Zieten, 1830); Seyed−Emami et slightly flexuous, ventrolaterally strongly projecting forward. al. 2005: 360, fig. 6C, D, F. Body whorl about 3/4 of the last whorl. Material.—Several specimens from Kuhe Bashm (050511−6). Dimensions (in mm) Dimensions (in mm) Specimen D U H W Specimen D U H W 050511−3/1 (holotype) 30 42 34 24 (end of body−chamber) 050511−6/3 33 30 45 26 25 40 36 26 Description and discussion.—See Seyed−Emami and Nabavi 14−2−3 (hypotype) 27 41 36 24 (1985: 266) and Seyed−Emami et al. (2005). 7−21−1 27 41 33 23 050511−3/6 (paratype) 31 40 35 – Stratigraphic and geographic range.—Kuhe Bashm, level VI. Late Toarcian Pleydella aalensis Zone. Description.—Small (D: 27–32 mm), evolute microconchs with rectangular to high−ovate whorl cross−section. The venter Pleydellia (Pleydellia) buckmani Maubeuge, 1947 is tectiform with a distinct keel, persisting up to the end of Fig. 5F, G. body whorl. Ribs are slightly flexuous, relatively coarse, spa− 1947 Pleydellia Buckmani; Maubeuge 1947: 76, pl. 2 (upper figures). ced, and projecting strongly forward ventrolaterally. Towards 2005 Pleydellia (Pleydellia) buckmani Maubeuge, 1947; Seyed−Emami the end of the body whorl the ribs become finer, denser and ir− et al. 2005: 362, fig. 6A, B, G. regularly paired. The body whorl occupies about 3/4 of the last Material.—Seven specimens from Kuhe Bashm (050511−5, whorl and carries elongated, spatula−like lappets. 050511−6). Discussion.—The new species is intermediate between P. Dimensions (in mm) schaireri, P. explanata (Buckman 1904: suppl. 104, pl. 22: Specimen D U H W 28–30), and P. tabulata (Buckman 1904: suppl. 185, pl. 22: 050511−6/2 27 26 47 26 25–27). From the closely related P. schaireri the new species 050511−6/3 34 25 45 25 differs in having coarser and wider spaced ribs. Compared to Description and discussion.—See Seyed−Emami and Nabavi P. explanata and P. tabulata the new species is less coarsely (1985: 265) and Seyed−Emami et al. (2005). ribbed and its final size is probably smaller. Similarly, the new taxon differs from P. tectiforme Elmi and Caloo, 1985 by its Stratigraphic and geographic range.—Kuhe Bashm, level finer ribbing and distinctly smaller final size. VI, Late Toarcian, Pleydella aalensis Zone. Stratigraphic and geographic range.—The new species was Pleydellia (Pleydellia?) ruttneri Seyed−Emami sp. nov. found, together with P. schaireri, P. explanata, and several Fig. 5L, M. specimens of the Dumortieria radiosa/moorei group, in a sin− Type material: The holotype (050511−6/9) is a nearly complete shell. gle concretion from Kuhe Bashm, level V. Paratype: A fragmentary specimen (050511−6/10).

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Type horizon: Shemshak Group, Upper Toarcian, Pleydella aalensis 2001 Pleydellia (Cotteswoldia) fuselieri; Rulleau and Elmi in Rulleau Zone, Kuhe Bashm section level VI at 270 m (Fig. 2). et al. 2001: 77, pl. 16: 7, 8. Type locality: Kuhe Bashm−e−Dehsufian, 13.5 km east of Shahmirzad, Material.—A one−side preserved specimen from Kuhe Bashm about 25 km north of Semnan. (050511−6/1). Derivation of the name: In honour of the Late Dr. Anton Ruttner (1911–2006), who contributed much to the geology of east−central Iran. Dimensions (in mm) Specimen D U H W Material.—Three specimens from Kuhe Bashm (050511−6). 050511−6/1 ~46 ~43 ~33 ~30 Dimensions (in mm) Description.—Evolute form with an ovate whorl cross−sec− Specimen D U H W tion, slightly higher than wide, and with a low, blunt keel. 050511−6/9 (holotype) 31 ~34 ~39 ~25 (at the end of phragmocone) Ribs are single, strong, and well spaced. Ventrolaterally, the 38 ~35 ~37 ~24 (at the end of body whorl) ribs bend slightly forward and fade on the fairly broad venter. Description.—The holotype (Fig. 5M1,M2) is a slightly Discussion.—Except for the slightly coarser ribbing and wider crushed microconch with rather short lappets and parts of the umbilicus, our specimen closely matches P. (C.) fuselieri. original shell. The body whorl begins at a diameter of 40 mm and occupies about 1/2 of the last whorl. It is moderately Stratigraphic and geographic range.—Kuhe Bashm, level evolute, with nearly parallel flanks and a rectangular to ovate VI. Together with P. aalensis and P. subcompta from the whorl cross−section. The venter is distinctly tectiform, with a Late Toarcian Pleydella aalensis Zone. narrow and sharp keel, which persists to the end of the body Pleydellia (Cotteswoldia) bifax Buckman, 1904 chamber. The umbilicus is shallow, with a nearly vertical Fig. 5P. wall. The ribs are fairly fine, dense and sinuous. They start at 1904 Cotteswoldia bifax; Buckman 1904: suppl. 136, fig. 110 A. the seam and project strongly on the venter forming an angle 2005 Pleydellia (Cotteswoldia) bifax Buckman, 1904 sensu Rulleau and end at the keel. Some ribs are irregularly paired on the and Elmi, 2001; Seyed−Emami et al. 2005: 362, fig. 6K, L. body whorl. Towards the end of the body chamber the rib− bing becomes slightly finer and denser. Material.—One crushed specimen from Kuhe Bashm (050511−6/5). Discussion.—The new species can be considered as a micro− conch belonging to the P. aalensis group. The short lappets Description and discussion.—See Seyed−Emami et al. (2005). look very much like those of P. aalensis figured by Buckman Stratigraphic and geographic range.—Kuhe Bashm, level (1890: pl. 32: 3), but the ribbing is different. The species also VI. Late Toarcian, Pleydella aalensis Zone. differs from the microconchs of P. aalensis figured by Hen− rique and Ureta (2002: 150, fig. 93). The parallel flanks and the Subfamily Leioceratinae Spath, 1936 fastigate venter with rather fine and partly pair−wise bundled Genus Leioceras Hyatt, 1867 ribs is reminiscent of Cotteswoldia and Walkeria. However, it cannot be assigned to any known species of these subgenera. Leioceras opalinum (Reinecke, 1818) Fig. 6C. Stratigraphic and geographic range.—The new species was found on a slab, together with Pleydellia (P.) buckmani, from 1818 Nautilus opalinum; Reinecke 1818: 55, pl. 1: 1, 2. 1967 Leioceras opalinum (Reinecke) 1818; Seyed−Emami 1967: 48, the (uppermost?) Late Toarcian, Pleydella aalensis Zone. pl. 1: 12; pl. 7: 3a, b. 1987 Leioceras opalinum (Reinecke), 1818; Goy and Ureta 1987: 216, Subgenus Cotteswoldia Buckman, 1902 pl. 1: 1–13; text−figs. 2, 3 (with synonymy). Pleydellia (Cotteswoldia) fuselieri Rulleau and 2001 Leioceras (Leioceras) opalinum (Reinecke); Rulleau et al. 2001: pl. 20: 4. Elmi, 2001 2004 Leioceras opalinum (Reinecke, 1818); Myczyński 2004: 73, figs. Fig. 6A. 26/8, 27/5.

Fig. 6. Upper Toarcian to Bajocian ammonoids from the Shemshak Group. A. Pleydellia (Cotteswoldia) fuselieri Rulleau and Elmi, 2001, Kuhe ® Bashm−e−Dehsufian, 050511−6−1, Pleydella aalensis Zone, Upper Toarcian; lateral (A1) and cross−section (A2) views. B, E. Graphoceras (Ludwigella) cornu Buckman, 1887, Kuhe Bashm−e−Dehsufian, Otoceras concavum Zone, Upper Aalenian. B. 050511−15/9; lateral (B1) and ventral (B2) views. E. 050511−15/8; lateral (E1) and ventral (E2) views. C. Leioceras opalinum (Reinecke, 1818), Kuhe Bashm−e−Dehsufian, 050511−7/10, Leioceras opalinum Subzone, Leioceras opalinum Zone, Lower Aalenian; lateral (C1) and ventral (C2) views. D, F. Graphoceras (Ludwigella) cf. rudis (Buckman, 1889), Sharif−Abad, Otoceras concavum Zone, Upper Aalenian. D. 050512−11a/13; lateral (D1) and ventral (D2) views. F. 050512−11/4; lateral (F1) and ventral (F2) views. G, I. Leioceras comptum (Reinecke, 1818); Kuhe Bashm−e−Dehsufian, Leioceras comptum Subzone, Leioceras opalinum Zone, Lower Aalenian. G. 050511−9/4; lateral (G1) and ventral (G2) views. I. 050511−9/5; lateral (I1) and ventral (I2) views. H. Graphoceras (Graphoceras) decorum Buckman, 1898, Sharif−Abad, 050512−11/8, Otoceras concavum Zone, Upper Aalenian; lateral (H1) and ventral (H2) views. J. Graphoceras (Grapho− ceras) concavum J. Sowerby, 1815, Sharif−Abad, 050512−12/1, Otoceras concavum Zone, Upper Aalenian, lateral view. K. Stemmatoceras? sp., Sharif−Abad, 050512−13, Middle Bajocian, lateral view. L. Erycites aff. sphaeroconicus Buckman, 1922, Kuhe Bashm−e−Dehsufian, 050511−7/1, Leioceras opalinum Zone, Lower Aalenian; lateral (L1) and ventral (L2) views. M. Bredyia alleoni (Dumortier, 1874), 050511−8, Leioceras opalinum Zone, Lower Aalenian; lateral (M1) and ventral (M2) views. N. Accardia aff. diadematoides (Mayer, 1871), Sharif−Abad, 050512−11/10, Middle Aalenian; lateral (N1) and apertural (N2) views. Arrows indicate onset of body chamber. SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 253

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Material.—A small specimen from Kuhe Bashm (050511− variation of G. (G.) concavum as given by Contini (1969) 7/10). and Caloo (1971). Description.—Involute Leioceratinae with high−ovate to lan− Stratigraphic and geographic range.—Kuhe Bashm, level ceolate whorl cross−section and a sharp keel. Umbilical border IX; Sharif−Abad, level G. Late Aalenian, Otoceras concavum is rather sharp, with an indistinct peri−umbilical depression. Zone. Ornamentation consists of fine and sinuous striae. Stratigraphic and geographic range.—Kuhe Bashm, level Graphoceras (Graphoceras) decorum Buckman, 1904 VII. Together with Bredyia from the Early Aalenian, Leio− Fig. 6H. ceras opalinum Zone, Leioceras opalinum Subzone. 1904 Graphoceras decorum; Buckman 1904: p. 98, pl. 15: 3, 4. 2004 Graphoceras decorum Buckman, 1888; Myczyński 2004: 100, Leioceras comptum (Reinecke, 1818) fig. 33/4. Fig. 6G, I. 2006 Graphoceras (Graphoceras) decorum Buckman, 1902; Seyed− Emami et al. 2006: 268, figs. 5/5a, b, 12a, b, 18. 1818 Nautilus comptus; Reinecke 1818: 57, pl. 1: 5, 6. 2005 Leioceras comptum (Reinecke, 1818); Seyed−Emami et al. 2005: Material.—Eight fragmentary specimens from Sharif−Abad: 365, fig. 7D, J. 050512−11 (11/1–11/8). Material.—Six specimens from Kuhe Bashm (050511−9/2– Dimensions (in mm) 050511−9/5, 050511−12/1, 050511−12/2). Specimen D U H W 050512−11/8 35 20 49 – Dimensions (in mm) Specimen D U H W Description and discussion.—See Seyed−Emami et al. (2006). 050511−9/5 54 24 44 19 Stratigraphic and geographic range.—Sharif−Abad, level G. 050511−9/4 56 16 48 21 Late Aalenian, Otoceras concavum Zone. Description and discussion.—See Seyed−Emami et al. (2005). Subgenus Ludwigella Buckman, 1901 Stratigraphic and geographic range.—Kuhe Bashm, level VII. Together with Planammatoceras cf. planinsigne (Vacek, Graphoceras (Ludwigella) cornu (Buckman, 1887) 1886) from the Early Aalenian Leioceras opalinum Zone Fig. 6B, E. (Leioceras comptum Subzone). 1887 Ludwigia cornu; Buckman 1887: pl. 4: 3, 4. 1969 Graphoceras (Ludwigella) cornu (Buckman, 1887); Contini 1969: Subfamily Graphoceratinae Buckman, 1905 73, pl. 5: 8, 9; pl. 12: 13–15, 17; pl. 24: 55–57; text−figs. 20–23 (with synonymy). Genus Graphoceras Buckman, 1898 1971 Graphoceras (Ludwigella) cornu (Buckman, 1887); Caloo 1971: Subgenus Graphoceras Buckman, 1898 pl. 1: 3–6, 10–12; pl. 2: 16, 19; pl. 3: 23–28, 30, 31. 2004 Graphoceras cornu (Buckman, 1887); Myczyński 2004: 102, Graphoceras (Graphoceras) concavum figs. 29/4, 30/8. (J. Sowerby, 1815) Material.—Three specimens from Kuhe Bashm (050511− Fig. 6J. 15/1, 050511−15/8, 050511−15/9). 1815 Ammonites concavus; J. Sowerby 1815: 274, pl. 94. Dimensions (in mm) 1967 Ludwigia (Graphoceras) concava concava (Sowerby) 1815; Specimen D U H W Seyed−Emami 1967: 66, pl. 2: 5; pl. 8: 5. 050511−15/9 26 ~32 ~43 ~32 1969 Graphoceras (Graphceras) concavum (Sowerby); Contini 1969: 050511−15/8 29 29 ~44 ~29 61, pl. 5: 3–6; pl. 21: 1–9; pl. 22: 1–3; pl. 24: 48–51; text−figs. 16, 17 (with synonymy). Description.—Moderately involute Graphoceratinae with 2001 Graphoceras (Graphoceras) concavum (Sowerby); Rulleau et al. high−ovate, slightly fastigate whorl cross−section and a sharp 2001: pl. 23: 1–3. keel. The ribbing is strongly falcate. The prorsiradiate pri− 2004 Graphoceras concavum (J. Sowerby, 1825); Myczyński 2004: mary ribs bifurcate mostly within the inner half of the flank. 99, fig. 33/1. The secondary ribs are strongly rursiradiate, slightly concave Material.—Four fragmentary specimens from Sharif−Abad and nearly angular to the primaries. (050512−11/1–050512−11/4) and three fragmentary specimens Discussion.—Our specimens falls well within the range of from Kuhe Bashm (050511−15/2, 050511−15/4, 050511−15/6). variation of the species as given by Contini (1969: especially Description.—The figured specimen (Fig. 6J) is a crushed pl. 12: 5). member of the Graphoceratinae with parts of the original Stratigraphic and geographic range.—Kuhe Bashm, level shell preserved. It is relatively involute, with a high−ovate, IX. Together with Graphoceras (G.) concavum from the compressed whorl cross−section and a sharp keel. The rib− Late Aalenian, Otoceras concavum Zone. bing is strongly anguliform−falcate. The last preserved whorl is probably part of the body chamber. It egresses slightly Graphoceras (Ludwigella)cf.rudis (Buckman, 1889) with a distinct peri−umbilical depression. Fig. 6D, F. Discussion.—The figured specimen falls within the range of 1889 cf. Ludwigia rudis; Buckman 1889: 103, pl. 15: 12. SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 255

1967 cf. Ludwigia (Ludwigella) rudis Buckman 1889; Seyed−Emami 2006 aff. Accardia diadematoides (Mayer, 1871); Seyed−Emami et al. 1967: 61, pl. 2: 3; pl. 7: 16. 2006: 269, figs. 5/8a, b, 16a, b (with synonymy). 1969 cf. Graphoceras (Ludwigella) rudis (Buckman) 1889 emend.; Material.—A specimen preserved one side from Sharif−Abad Contini 1969: 71, pl. 5: 7; pl. 22: 6–12; pl. 14: 52–53; text−fig. 19 (with synonymy). (050512−11/10). 2001 cf. Graphoceras (Ludwigella) rudis Buckman; Rulleau et al. Dimensions (in mm) 2001: pl. 23: 6a, b, 7a, b. Specimen D U H W Material.—Two fragmentary specimens from Sharif−Abad 050512−11/10 57 35 39 ~39 76 34 39 ~32 (050512−11/4, 050512−11a/13). Description.—Coarsely ribbed Hammatoceratinae with a Description.—The fragmentary specimens are relatively evo− high hollow−floored keel. The whorl cross−section on the in− lute, with a rectangular−ovate whorl cross−section, a broad ner whorls is broad−ovate, becoming triangular high−ovate at venter and a low blunt keel. The ornamentation consists of the last preserved whorl. On the inner whorls the ribbing con− falcate, blunt ribs, irregularly bifurcating near to the umbilicus. sists of short and blunt primaries ending in strong tubercles Discussion.—The fragmentary specimens is closely compa− (about 15 tubercles at D = 50 mm). From a diameter of 50 rable to the specimens figured by Rulleau et al. (2001: pl. 23: mm onwards, the nodes give way to short, strong, and radiate 6, 7). primaries, often bifurcating below the mid−flank into slightly Stratigraphic and geographic range.—Sharif−Abad, level G. sinuous secondaries. On the venter the ribs curve slightly for− Late Aalenian, Otoceras concavum Zone. ward and end at the keel. Discussion.—The figured specimen matches well the origi− Family Hammatoceratidae Buckman, 1887 nal of Mayer (1871) figured by Rieber (1963: pl. 8: 5, 7). Subfamily Hammatoceratinae Buckman, 1887 Compared with a larger specimen from the Shemshak Group Genus Bredyia Buckman, 1910 of the Tazareh section, described by Seyed−Emami et al. Bredyia alleoni (Dumortier, 1874) (2006), the present specimen has a greater number and more densely spaced tubercles. Fig. 6M. Stratigraphic and geographic range.—Sharif−Abad, level G. 1874 Ammonites alleoni; Dumortier 1874: 259, pl. 52: 3, 4. Late Aalenian, Otoceras concavum Zone. 1963 Parammatoceras alleoni (Dumortier, 1874); Elmi 1963: 55, pl. 8: 1–3; text−fig. 22. 2001 Bredyia alleoni (Dumortier, 1874); Rulleau et al. 2001: pl. 25: Family Eryceritidae Spath, 1928 10a, b. Genus Erycites Gemmellaro, 1886 2002 Bredyia alleoni (Dumortier, 1874); Cresta and Martinez in Pavia and Cresta 2002: 192, figs. 125–126. Erycites aff. sphaeroconicus Buckman, 1922 Fig. 6L. Material.—Two specimens from Kuhe Bashm (050511−7/2, 050511−8). 1922 aff. Erycites sphaeroconicus; Buckman 1922: pl. 315. Dimensions (in mm) Material.—A specimen preserved on one−side from Kuhe Specimen D U H W Bashm (050511−7/1). 050511−8 73 ~27 ~45 ~34 Dimensions (in mm) Description.—The figured specimen is slightly crushed. It is Specimen D U H W relatively involute with a high−ovate to triangular whorl 050511−7/1 62 27 38 ~65 cross−section and a narrow and fairly high keel. The flanks Description.—Fairly involute and highly depressed Erycites, converge towards the relatively broad venter. The ribbing is with a deep umbilicus, a broad and cadicone whorl cross−sec− coarse and sinuous with strong and nearly radiate primaries, tion and a flat keel. The ribbing is relatively strong and nearly which often trifurcate within the lower third of the flank. On rectiradiate.The straight primary ribs usually trifurcate ven− the venter the ribs bend forward and nearly reach the keel. trolaterally, without any tubercles. The secondary ribs con− tinue straight onto the broad venter and end nearly vertically Discussion.—The differences to the closely related B. sub− oriented with respect to the flat keel. About 11 primaries and insigne (Oppel, 1836) and B. iranica Seyed−Emami have 33 secondaries have been counted on the last preserved been discussed by Senior (1977) and Seyed−Emami (1987). half−whorl (ratio 1:3). Stratigraphic and geographic range.— Kuhe Bashm, level Discussion.—The described specimen is most probably a new VII. Late Aalenian, Leioceras opalinum Zone. Bredyia alleoni species, being characterized by its highly depressed and was found in the beds with Leioceras opalinum. cadicone whorl cross−section. Concerning the narrow umbili− Genus Accardia Cresta, 1997 cus and the depressed whorls, it can be somehow compared to the inner whorls of the group of Erycites fallax (Benecke, Accardia aff. diadematoides (Mayer, 1871) 1865), which has been considered a synonym of E. fallifax Fig. 6N. Arkell, 1950 by Callomon and Chandler (1994: 21). Com− 1871 aff. Ammonites diadematoides; Mayer 1871: 243, pl. 8: 9. pared to the latter our specimen is clearly more involute, much

http://app.pan.pl/acta53/app53−237.pdf 256 ACTA PALAEONTOLOGICA POLONICA 53 (2), 2008 more depressed and has a coarser ribbing. Concerning the nar− indicates the existence of direct but episodic marine connec− row umbilicus and the broad, cadicone whorls, our specimen tions and faunal exchange between the two areas (Seyed− can be best compared to Erycites aff. sphaeroconicus Emami 1988). The faunal migration routes during the Early Buckman, 1922 of Rulleau et al. (2001: pl. 27: 7a, b). Other Jurassic and earliest Middle Jurassic followed most probably similar taxa are E. barodiscus Gemmellaro, 1886 in Cresta the epicontinental platforms at the southern margin of the (1997: pl. 3: 5) and E. involutus Prinz, 1904 in Prinz (1904: 90, Eurasian landmass (Fig. 7). pl. 32, pl. 33: 7) and Géczy (1966: 103, pl. 25: 5). From these, Marine intercalations and faunas within the Shemshak our specimen is distinguished again by more depressed and Group are apparenly related to transgressive episodes in the cadicone whorls. Norian, Late Sinemurian, Late Pliensbachian, Toarcian, and Stratigraphic and geographic range.—Erycites is a typical Aalenian. Strikingly the transgressive phases do not necces− Mediterranean taxon, being only known sporadically from sarily follow the global sea−level rise and fall (Hardenbol et the Kerman area of southeastern Central Iran (Seyed−Emami al. 1998; Hallam 2001), but apparently were greatly influ− 1967, 1971). This is the first record of the genus from the enced by the local and regional synsedimentary tectonic ac− Alborz Range. The single specimen was found at Kuhe tivity (Fürsich et al. 2005). Bashm (level VII) above the beds with Pleydellia, co−occur− On the whole, the ammonite fauna of the Shemshak Group ring with Leioceras opalinum from the Late Aalenian Leio− is rather poor and discontinuously distributed, with low spe− ceras opalinum Zone. cies richness and low generic diversity but a strong dominance of certain taxa (one or a few genera). The abundance and di− Superfamily Neumayr, 1875 versity of the fauna is evidently related to periods of reduced siliciclastic input (starvation) in connection with sea level Family Stephanoceratidae Neumayr, 1875 rises. These periods are usually indicated by intercalations of Genus Stemmatoceras Maschke, 1907 calcareous beds, which are minor constituents within the over− Stemmatoceras? sp. whelmingly siliciclastic sediments of the Shemshak Group. Fig. 6K. In total, 236 ammonite specimens have been collected from the sections north of Semnan, comprising 62 taxa. The Material.—A single specimen from Sharif−Abad (050512− relative abundances at the family level are: Phylloceratinae 13). (<1%), Cymbitidae (<0.5%), Echioceratidae (~2%), Amal− Discussion.—A fragment of a large and coarsely ribbed theidae (~8%), Dactylioceratidae (6%), Hildoceratide (8.5%), Stephanoceratidae was found at Sharif−Abad (level H), Graphoceratidae (63%), Hammatoceratinae (10%), Eryciti− which may be a Stemmatoceras from the Middle Bajocian. dae (<0.5%), and Stephanoceratidae (<0.5%). Summing up, Stephanoceratidae are common in the Badamu Formation of besides few endemic taxa (~6%), the fauna is closely related the Kerman area (Seyed−Emami 1967, 1971, 1988), but have to northwestern Europe (Subboreal Province) with minor been never reported with certainty from the Alborz Range. Tethyan (Mediterrranean) elements. The few representatives of Tethyan elements are, without exception, taxa that also oc− cur in northwestern Europe. The nearly total absence of Palaeogeography and Lytoceratinae and the scarcity of Phylloceratinae (<1%), as elsewhere in North and Central Iran, is remarkable. Contrary palaeobiogeography to the situation in the Shemshak Group, Phylloceratidae are very well represented in Middle and Upper Jurassic strata of After closure of the Palaeotethys in the Late Triassic, the Iran the Alborz region (Dalichai and Lar formations) since the Plate (Central and North Iran) occupied a position at the south− Late Bajocian (up to 50% of the total fauna), and the Tethyan ern margin of Eurasia (Seyed−Emami 2003). Close lithologic (Submediterranean) influence is also much more evident and and faunistic relationships between North and Central Iran stronger (Seyed−Emami et al. 2001). This indicates environ− during deposition of the Shemshak Group indicates that the mental changes (e.g., in bathymetry and sea−water tempera− two areas were palaeogeographically closely related, probably tures) and probably the existence of new marine connections. forming a kind of archipelago. According to palaeogeographic Even though the diversity of the taxa within the Shem− maps of the (Dercourt et al. 1993, 2000) North shak Group is much lower than in age−equivalent strata of Iran (Alborz) occupied a fairly high latitudinal position of ap− northwestern and central Europe, the Graphoceratidae (con− proximately N 44°, at the northeastern margin of the Western cerning the number of the specimens as well as the number of Tethys (Fig. 7). During the Middle Jurassic (Middle Callo− taxa) make up the bulk of the fauna. The subfamily Dumor− vian) it shifted to a lower latitude of about N 30°,which tierinae alone accounts for more than 50% of the total fauna. roughly corresponds to the latitude of the northwest European The low relative abundance of Hammatoceratidae compared Archipelago. with southeastern Central Iran is noteworthy as is the scarcity The close palaeobiogeographic relationship of the am− of Hildoceratidae, except Grammoceratinae. Of special palaeo− monite faunas with those of Northwest Europe and the north− biogeographic interest is the presence of Amaltheidae, be− western Tethys during the Jurassic and systems cause of their strictly boreal distribution (Smith et al. 2001). SEYED−EMAMI ET AL.—MIDDLE JURASSIC AMMONOIDS FROM IRAN 257

Fig. 7. Palaeogeography of the western and central peri−Tethyan area showing inferred ammonite migration routes (modified after Dercourt et al. 2000). The asterisk indicates the position of the ammonite fauna of this study.

A boreal influence in central and northeastern Iran is again 1985; Seyed−Emami 1987; Seyed−Emami and Hosseinzadeh evident in the and , indicated by the 2006, and this study). They comprise the families Cymbitidae, presence of Leymeriellidae, Hoplitidae, and Schloenbachia Echioceratidae, Amaltheidae, Dactylioceratidae, Hildocerati− (Seyed−Emami 1988). Remarkably, there is no faunal rela− dae, Graphoceratidae, Hammatoceratidae, Erycitidae, and tionship at all with the southern Tethys and southwestern Stephanoceratidae. As in northwestern and central Europe Iran (Zagros). (Callomon and Chandler 1994; Myczyński 2004) and else− where in Iran (Seyed−Emami et al. 2005), members of the fam− ily Graphoceratidae make up the bulk of the fauna (>60%). Of Conclusions these, the subfamily Dumortierinae alone accounts for more than one−third of the entire taxa. Noteworthy is also the relative Of the various sections of the Shemshak Group in the south− abundance of Hammatoceratidae (~10%), which usually are eastern Alborz Mountains studied by our team (Tazareh: much less common in the Alborz region. As usual, Lytocera− Fürsich et al. 2005; Seyed−Emami et al. 2006; Jajarm: Seyed− tidae are entirely absent and Phylloceratidae form less than 1% Emami et al. 2005), the sections east of Shahmirzad so far con− of the total fauna. Of special palaeobiogeographic interest is tain the most abundant marine intercalations. Apart from the presence of Amaltheidae, because of their boreal and sub− short−lived marine ingressions in the Norian (unpublished boreal distribution (Smith et al. 2001). data), Late Sinemurian, and Late Pliensbachian, the most ex− As previously discussed (Seyed−Emami 1988; Seyed− tensive and long−lasting marine transgression occurred during Emami et al. 2001, 2005, 2006) the ammonite faunas from the Toarcian and Aalenian, as is the case in the most parts of the the Shemshak Group are closely related to those occurring in Iran Plate. Concerning the number, diversity, and preservation northwestern and central Europe, the Northwest European quality of the ammonite faunas, the sections east of Shah− Province of Dean et al. (1961) and Cariou and Hantzpergue mirzad are unique in the Alborz Range. Up to now, more than (1997). They exhibit minor relationships with the Mediterra− 60 taxa have been described from the Shemshak Group (Table nean Province but none with faunas from the southern hemi− 1; Nabavi and Seyed−Emami 1977; Seyed−Emami and Nabavi sphere (southwestern Iran and southern Tethys).

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Cresta, S. 1997. Hammatoceratidi aaleniani di Monte Rice (Sicilia occidentale, Acknowledgements Italia). Bolletino del Servizio Geologico d'Italia 114: 27–56. Dagis, A.A. 1976. Upper Pliensbachian ammonites (Amaltheidae) of north− The present study is part of a joint research programme of University of ern Siberia [in Russian]. Trudy Instituta Geologii i Geofiziki 309: 1–79. Tehran (Centre of Intelligence) and the Institute of Palaeontology of Dean, W.T., Donovan, D.T., and Howarth, M.K. 1961. The Liassic ammonite Würzburg University, within an institutional partnership sponsored by the zones and subzones of the Northwest European Province. Bulletin of the Alexander von Humboldt Foundation. We acknowledge logistic support British Museum (Natural History), Geology Series 4 (10): 435–505. by the Geological Survey of Iran and the hospitality of Enayatollah Dedual, E. 1967. Zur Geologie des mittleren und unteren Karaj−Tales, Ranjbar (Center of Coexistence with Deserts, University of Tehran, Iran), Zentral−Elburz (Iran). Mitteilungen, Geologisches Institut ETH und Vahid Etemad and Jaafar Fathi (Faculty of Natural Resources, University Universität Zürich, Neue Folge 76: 1–123. Dercourt, J., Ricou, L.E., and Vrielynck, B. (eds.) 1993. Atlas Tethys of Tehran) during our stay in Semnan and Noshahr. Majid Khazai and Paleoenvironmental Maps. 307 pp. Gauthier−Villars, Paris. Hossein Mohamadkhani (Geological Survey of Iran) are thanked for their Dercourt, J., Gaetani, M., Vrielynck, B, Barrier, E., Biju−Duval, B., Brunet, help in the field, KS−E thanks Reinhold Leinfelder (Humboldt Museum, M.F., Cadet, J.P., Crasquin, S., and Sandulescu, M. (eds.) 2000. Atlas Berlin, Germany) for providing research facilities during his stay in Mu− Peri−Tethys palaeogeographical maps. 268 pp. CCGM/ CGMW, Paris. nich, Gerhard Schairer (Bayerische Staatssammlung für Paläontologie Dommerggues, J.−L., Meister, C., and Mouterde, L. 1997. Pliensbachien. In: und historische Geologie, Munich, Germany) for inspiring discussions, E. Cariou and P. Hantzpergue (eds.), Biostratigraphie du Jurassique and Georg Janssen (Bayerische Staatssammlung für Paläontologie und ouest−européen et méditerranéen. Bulletin du Centre Recherches Explo− historische Geologie) for his excellent photographic work. Finally, we ration−Production, d'Elf−Aquitaine, Mémoire 17: 15–23. thank the reviewers, Kevin Page (Plymouth, U.K.), and Paul L. Smith Dommergues, J.−L., Meister, C., Bonneau, M., Poisson, A., and Vrielinck, B. (Vancouver, Canada) for their constructive remarks. 2005. Les ammonites pliensbachiennes des nappes lyciennes (Turquie méridionale). 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